Machine-screw



O. A. SMITH.

MACHINE SCREW.

APPLICATION FILED MAY I6, 1919.

Patented Feb. 10,1920.

UNITED STATES PATENT OFFICE.

OSCAR A. SMITH, OF CLEVELAND, OHIO, ASSIGNOB- TO THE NATIONAL ACME COMPANY,

OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

MACHINE-SCREW.

Specification of Letters Patent.

Patented Feb. 10, 1920.

Application filed May 16, 1919. Serial No. 297,692.

To all whom it may concern:

Be it known that I, OSCAR A. SMITH, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented certain new and useful Improvements in Machine Screws, of which the following is a specification.

This invention relates to machine screws, such as fillister head or round head or col lar machine screws, the object of the invention being to provide a headed machine at the margins of such convexed driving.

portions.

In the present improvement however,'the diameter of the recesses is materially smaller than the arc of the convexed driving portions at the margins of the head notwithstanding which, however, a driving tool such as is shown in the present improvement, can be used with equal facility to drive the set screw shown in my said patent, which important result has been Worked out after considerable experimentation.

In the drawings accompanying and forming part of this specification, Figure 1 is a top view of a round head machine screw; Fig. 2 is a top view of a fillister head machine screw; Fig. 3 is a side View of a round head machine screw; Fig. 4 is a side View of a fillister or oval head machine screw; andFig. 5 is a perspective View of a headed machine screw and the mating end of its wrench.

Similar characters of reference indicate corresponding parts in the several figures of the drawings.

There are of course many. forms of headed machine screws in common use, practically all of whlch have a common screw. driver slot, and it is of course ditficult to tighten or set them home strong enough with a screw driver and various attempts have been made to improve these styles of machine screws, but for various reasons they have not been found entirely satisfactory.

By means of the present improvement how-- ever, the head of the machine screw is eX- ceptionally strong, and while the wrench or driving tool is sufliciently strong to properly set the screw home for all practical requirements, yet the wrench is the weaker member and it should be at least of substantially no greater strength than the driving portion of the screw and there'are no sharp corners either on the wrench or on the tang to afford opportunity for breakage or peening oif.

This improved machine screw shown in the drawings comprises a head 2 and a threaded shank3, the headin Fig. 1 be ing known as a round head machine screw while that in Fig, 2 is known as a fillister or oval head machine screw. Formed in the head are a pair of radial recesses 4, each having parallel straight sides 5 and a curved inner face 6 terminating short of the vertical axis of the head thereby forming a pair of connected conveXed portions 7, the arcof each of which at the margin of the head 8is greater than the diameter 9 of said recesses and the depth of which recesses is materially less than the depth of the head. Thus in the present improvement the convexed driving portions of the tang have diameters materially greater than the diameter of the radial recesses and yet the structure is such that the driving tool herein shown, and which is adapted to fit such radial recesses, can be used with equal facility in driving the set screw shown in my said patent, so that it is unnecessary to furnish a special driving tool for the set screw of said patent and also for the machine screw of the present improvement.

The wrench shown in Fig. 5 is provided with a groove '10 adapted to mate with the tang or driving member of this improved machine screw, which groove forms a pair of driving portions 11 having generally the shape of the radial recesses of the driving convexed formation of the wrench or driving tool provides a very effective interlock between these two members, so that the possibility of twisting off the driving portion of the screw is eliminated. Not only this, but the turning movement of the wrench or driving tool, should there be any play between its driving portions and the tang of the machinescrew, Will cause the interlocked portions to effectively engage each other to prevent slippage of one relatively to the other and thus avoid the twisting off of the tang or the eating off of the edges thereof.

The gist of the present improvement is the provision of a headed machine screw having a reinforced driving portion which will be as strong as, if not stronger than the means for tightening the screw, so that the heads cannot become peened or broken, and

which will avoid the common form of slot usually used, and which form of machine screw cannot be readily tightened home strain of the I claim as my invention:

1. A machine screw having a round head provided with straight sides, said head having in the top thereof a pair of radial recesses, each having parallel straight sides and a curved inner face terminating short of the vertical axis of the head to forma pair of connected convexed portions, the greatest diameter of each of which is greater than the greatest diameter of either of said recesses, and the depth of each of which recesses is less than the depth of said round head. a

2. A machine screw having a curved head provided with straight sides, said head having in its top a pair of opposed radial recesses to form a driving portion or tang gradually thickening outward from the axis of the screw to the margin of the head whereby the driving portion or tang is of greater width at the margin of the head than it is at the axis thereof thereby to bring the strain of setting the screw on the thickest portion of the tang and the arc of which thickest portion of the tang is materially greater than the arc of said radial recesses and the depth of each of which recesses is materially less than the depth of said straight sides of the head.

Signed at Cleveland, in the county of Guyahoga and State-of Ohio, this 12th day of May, 1919.

OSCAR A. SMITH. 

